To evaluate the safety and tolerance of the combination of adefovir dipivoxil at two comparative doses and nelfinavir plus saquinavir SGC administered orally versus the combination of adefovir dipivoxil and nelfinavir plus either AZT, 3TC, or d4T, versus the combination of adefovir dipivoxil and saquinavir SGC plus either AZT, 3TC, or d4T in HIV-1 infected patients with prior nucleoside reverse transcriptase inhibitor therapy but no prior exposure to prokease inhibitors. This study will also determine the proportion of patients whose plasma HIV-I RNA level falls below the level of detection (<500) at 20 weeks and the average reduction in HIV-I RNA from baseline through study week 20.